New South Wales Premier Gladys Berejiklian is standing firm on her opposition to pill testing, despite pleas from the family of a teenager who died of a suspected overdose after taking drugs at a music festival.

Central Coast woman Alex Ross-King, 19, on Saturday evening was rushed from the FOMO festival at Parramatta Park to Westmead Hospital where she subsequently died.

Police and NSW Health believe the teenager ingested substances before her death although a post-mortem and toxicology examination will confirm details.

Grandmother Denise Doig on Sunday said Alex was an adorable and loving teenager.

Alex Ross-King, 19, died after the FOMO festival in Sydney. Photo: Facebook

She wants Ms Berejiklian to introduce pill testing immediately so other families won’t suffer like hers.

“Premier please can we have this pill testing done,” Ms Doig told Network Ten.

“It’s such a small thing to do. It’s not hard (and) if it saves one life – one life is a life.”

But the Liberal Premier remained defiant, telling teens to simply say “No” to drugs.

Ms Berejiklian argued there’s no evidence that pill testing worked and that for every expert who supported it, there was “another few” that don’t.

“We are concerned by the unintended consequences of pill testing,” she told Nine’s Today Show on Monday.

“Pill testing could unfortunately give people a false sense of security.”

The Premier said young people needed to be better educated and told it’s OK to seek medical attention if something was wrong.

“The message to young people is do not take these tablets.”

Prime Minister Scott Morrison said it was a difficult issue with varying opinions, but ultimately one for the states to deal with.

“I am sure Gladys is looking at every option that is reasonable and has a way of getting the balance right,” he told the program.

“We don’t want to create a permissive culture around drugs in this country – we have to remember these are illegal drugs.”

Five people have now died in four months after taking drugs at NSW festivals.

Ms Ross-King’s uncle, Phil Clark, told Network Ten on Sunday his niece was an only child and the entire extended family was “grieving heavily”.

“Strong leadership isn’t always about sticking to an ideological decision or a position,” he said.

Pill testing allows people to anonymously submit samples for on-the-spot analysis to determine their composition.

A trial at a major Australian music festival in 2016 found two in three people wouldn’t consume a pill if a test showed it contained methamphetamine.

Friend Evan James paid tribute to Alex on Facebook on Sunday.

“Alex Ross-King to me was the definition of a kindred spirit, she had a deeper understanding of this earth and sadly this world didn’t deserve her,” he posted alongside a photo of him with Alex.

FOMO organisers said they were “deeply saddened” and stressed they proactively discouraged drug use.

“Our most heartfelt and sincerest condolences go out to her family and friends,” a spokeswoman said in a statement.

“Our anti-drug messaging began weeks ahead of the event and continued at the event itself.”

Ten people were hospitalised after the festival which almost 12,000 attended.

Police officers searched 146 people and of those 54 had drugs.

There were 36 arrests and two people were charged with drug supply – a 23-year-old man and an 18-year-old woman.

NSW Police Assistant Commissioner Mark Jones on Sunday said it was a “very tragic event”.

He said law enforcement didn’t want to be “the fun police” but hoped “to make festivals safe”.

Police said the drug seizures they made during FOMO were not linked to Alex’s death at this stage.

NSW Health warned MDMA and other party drugs carried risks.

“MDMA affects everyone differently but its lethal toxicity is well known,” the agency said in a statement.

“People should be aware of poisoning symptoms – a fast heartbeat, high body temperature, confusion and vomiting and get to medical help fast.

-AAP